1. Field of the Invention
The present invention is related to a method of changing a user equipment mobility state in the RRC connected mode, and more particularly, to a method of changing a user equipment mobility state in the RRC connected mode based on background traffic or monitor requirement.
2. Description of the Prior Art
The 3rd Generation Partnership Project (3GPP) has developed various wireless communication networks. A universal mobile telecommunications system (UMTS) or a global system for mobile communications edge radio access network (GERAN) is a 3rd generation (3G) network which adopts a wideband code division multiple access (WCDMA) technology capable of providing high frequency spectrum utilization, universal coverage, and high-speed/quality multimedia data transmission. In the UMTS network, a radio access network known as a universal terrestrial radio access network (UTRAN) includes multiple cells, commonly known as Node-Bs (NBs), for communicating with multiple user equipment (UE). Along term evolution (LTE) system is a 4th generation (4G) network which includes a new radio interface and radio network architecture capable of providing a high data rate, low latency, packet optimization, and improved system capacity and coverage. In the LTE network, a radio access network known as an evolved UTRAN (E-UTRAN) includes multiple evolved NBs (eNBs) for communicating with multiple UEs and a core network which includes a mobility management entity (MME), a serving gateway and other devices for non-access stratum (NAS) control.
According to 3GPP specifications, after selecting a public land mobile network identity (PLMN), the UE may perform a cell selection procedure and a cell reselection procedure in order to use related network services. The cell selection procedure allows the UE to quickly camp on a serving cell, thereby receiving system information from the PLMN, establishing radio resource control (RRC) links, accessing network via control channels, and receiving/replying paging messages. The cell reselection procedure allows the UE to camp on another target cell having better signal quality than the current serving cell for better performance.
Multiple application programs may be run on a UE at the same time. For example, a user may read an electronic book (E-book) on the UE with telecommunications application software being executed in the background environment. The execution of each application program may involve user interactive commands and/or non-user interactive commands. For example, since the user may issue commands for turning pages, making remarks or adding bookmarks while reading an E-book, the E-Book interface is a user interactive application program. Meanwhile, the telecommunications application software is a non-user interactive application program since it only causes background traffic. Background traffic includes keep-alive messages automatically sent by the UE to the base station, but does not involve any active commands issued by the user. Similarly, once the user switches to the interface of the telecommunications application software for browsing a new message, the telecommunications application software becomes a user interactive application program, while the E-Book interface executed in the background environment becomes a non-user interactive application program.
In a prior art wireless communication system, even if the user does not actively engage in any application program, the modem of the UE is still turned on by background traffic caused by non-user interactive application programs, thereby increasing power consumption. Even if user interactive application programs and non-user interactive application programs have different requirements for data latency, the prior art wireless communication system fails to change the mobility state of the UE accordingly, thereby causing high handover failure rate. Meanwhile, the current mobility state of the UE may not be able to meet the monitor requirement of the network, thereby causing unnecessary power consumption or high handover failure rate.